Navigating an interventional device

ABSTRACT

The present invention relates to navigating an interventional device. In particular, the invention relates to a system for navigating an interventional device within a tubular structure of an object, a method for navigating an interventional device within a tubular structure of an object as well as a computer program element and a computer-readable medium. In order to provide enhanced information to the user in an easily comprehensible manner while keeping the X-ray dose to a minimum, a system and a method for navigating an interventional device within a tubular structure of an object are provided, wherein the method comprised the following steps: a) Acquiring 2D X-ray fluoroscopy image data in one projection geometry of a region of interest of the tubular structure; b) detecting the interventional device in the 2D X-ray image; c) determining the 2D position of the interventional device in the 2D X-ray image; d) registering the at least one 2D X-ray image with a previously acquired 3D dataset of the region of interest of the tubular structure; e) mapping the determined 2D position of the interventional device to a position in the 3D dataset; f) extracting local 3D parameters of the tubular structure at the position of the interventional device; g) generating navigational information on behalf of the determined 3D position of the interventional device and the extracted local 3D parameters; and h) providing the navigational information to the user.

FIELD OF THE INVENTION

The present invention relates to navigating an interventional device. Inparticular, the invention relates to a system for navigating aninterventional device within a tubular structure of an object, a methodfor navigating an interventional device within a tubular structure of anobject as well as a computer program element and a computer-readablemedium.

BACKGROUND OF THE INVENTION

In order to use interventional devices in tubular structures where thelocation of the device is not visible to the user from the outside ofthe object, the user is provided with information about the location ofthe device in relation to the object. For example, during neurologicalinterventions, devices are routinely used in the treatment process ofdiseased vessels. In order to assist the physician, for example aneurosurgeon, with navigating a specific device to the diseased vesselsegment, the device and region of interest are visualized using X-rayimaging. For example, this is achieved by two-dimensional X-rayprojection images, a disadvantage of which is that the truethree-dimensional nature of the vessels is lost. This may lead todistorted visualization of, for example, vessel segment length, vesselbranching angles and vessel tortuosity. This may hamper navigation ofthe device through the vessels. An example for applying information fornavigation purposes is the so-called road mapping functionality. From anavailable 3D vessel representation, a projection image that matches thecurrent viewing angle of the X-ray apparatus is created. This artificialprojection image is then overlaid and registered on live X-ray fluoroimages to provide the physician with the road map during devicenavigation. For example, EP 0 809 211 A2 describes to form and store aseries of 2D X-ray images of an object, to form a 3D image, to extract arelevant structure from the 3D image and to calculate a series of thesynthetic 2D projection images of the extracted structure, wherein thestructure is projected with the same geometrical parameters as used forthe structure during the formation of the individual X-ray images.Further, the synthetic projection images and the processed X-ray imagesare superimposed.

SUMMARY OF THE INVENTION

However, the projected roadmap is still a 2D “flat” representation ofthe vessels which does not provide depth information. Additionally,overlaying the footprint of the vessels tends to clutter theinterventional image, which should be left as clean as possible.Further, it is a constant demand to provide detailed enhancedinformation.

Hence, there may be a need to provide enhanced information to the user,i.e. the operator, in an easily comprehensible manner.

According to an exemplary embodiment of the invention, the method and asystem for navigating an interventional device within a tubularstructure of an object is provided as further defined in the independentclaims.

According to an exemplary embodiment of the invention, a method fornavigating an interventional device within a tubular structure of anobject is provided, comprising the following steps: a) acquiring 2DX-ray fluoroscopy image data in one projection geometry of a region ofinterest of the tubular structure; b) detecting the interventionaldevice in the 2D X-ray image; c) determining the 2D position of theinterventional device in the 2D X-ray image; d) registering the at leastone 2D X-ray image with a previously acquired 3D dataset of the regionof interest of the tubular structure; e) mapping the determined 2Dposition of the interventional device to a position in the 3D dataset;f) extracting local 3D parameters of the tubular structure at theposition of the interventional device; g) generating navigationalinformation on behalf of the determined 3D position of theinterventional device and the extracted local 3D parameters; and h)providing the navigational information to the user.

One of the advantages is that, although only one projection is providedfor the X-ray fluoroscopy image, which one projection for itself doesnot provide any depth information, by mapping the determinedtwo-dimensional position to a position in the 3D data set it is stillpossible to derive the necessary three-dimensional information as abasis for the navigational information being provided to the user. Thenavigational information can thus assist the user, for example aphysician, to steer the device navigation, for example. By extractinglocal three-dimensional parameters, the interventional device serves asa pointer in the 3D data set or 3D volume. Since the two-dimensionalinformation is acquired by two-dimensional X-ray fluoroscopy images, itis possible to continuously acquire such images in order to continuouslytrack the two-dimensional device position and the relatedthree-dimensional position during the navigation process, providing thepossibility to communicate three-dimensional information to thephysician, or the user, in real-time.

For example, a neurosurgeon performs X-ray angiography on patients toinvestigate and diagnose neurology related diseases, for example in thehead region of a patient. For example, the neurosurgeon performs adiagnostic rotational angiographic scan. From the two-dimensionalprojection images acquired with this scan, a three-dimensionalrepresentation of the neuro vessels is created, which vessels show ahigh tortuosity. This three-dimensional representation can, for example,be used to support the diagnosis based on the two-dimensionalangiograms. The three-dimensional representation may also be acquired ona different imaging system, for example a CT scanner. When treatment ofthe patient is necessary, a device is navigated to the diseased vesselsegment. The device steering is done under the guidance of X-rayfluoroscopy. In order to benefit from the three-dimensional vesselinformation already available, the three-dimensional volume needs to beregistered to the fluoro images of the device and the vessels, forexample the neuro vessels. Registration can, for example, be achieved byusing the X-ray systems geometry information, and fluoro images of theneuro vessels enhanced with contrast agent. The three-dimensional volumecan be, but does not need to be segmented, for example, registration canbe done by matching ridgeness information in the two-dimensional fluoroand three-dimensional volume. During device navigation, the device isdetected and tracked in the fluoroscopy images such that its position inthe fluoro images is continuously known. This position is thencontinuously mapped to a unique position in the registeredthree-dimensional representation of the vessel. Three-dimensionalinformation of the vessel segment surrounding the device location canthen be presented, for example displayed on a screen, to a neurosurgeonto support navigation of the device.

The invention can be used in X-ray guided neuro vessels interventions,as described above. However, the invention can also be applied in anyX-ray guided intervention in which at least to some extent radiopaquedevices are used and three-dimensional information on the region ofinterest is available.

Since the two-dimensional X-ray fluoroscopy images are acquired in onlyone projection geometry, the navigational information is based on acomputed determination of a point in the three-dimensional data set forwhich the assumption that the point of the device is located within asegment of the tubular structure has the highest plausibility.

According to an exemplary embodiment of the invention, a system fornavigating an interventional device within a tubular structure of anobject is provided, the system comprising: an X-ray image acquisitiondevice; a processing unit; and an interface. The X-ray image acquisitiondevice is adapted to acquire 2D X-ray fluoroscopy image data in oneprojection geometry of a region of interest of the tubular structure.The processing unit is adapted to detect the interventional device inthe 2D X-ray image and to determine the 2D position of theinterventional device in the 2D X-ray image. The processing unit isfurther adapted to register the at least one 2D X-ray image with apreviously acquired 3D dataset of the region of interest of the tubularstructure and to map the determined 2D position of the interventionaldevice to a position in the 3D dataset. The processing unit is alsoadapted to extract local 3D parameters of the tubular structure at theposition of the interventional device and to generate navigationalinformation on behalf of the determined 3D position of theinterventional device and the extracted local 3D parameters. Theinterface is adapted to provide the navigational information to theuser.

According to an exemplary embodiment of the invention, the navigation ofan interventional device comprises guiding a user, for example aphysician such as a surgeon or interventional cardiologist performing amedical procedure.

According to an exemplary embodiment of the invention, the 2D X-rayfluoroscopy image data comprises a sequence of two images with the sameprojection geometry. The 3D position is mapped by extracting adetermined point of the interventional device in the two 2D images.

According to an exemplary embodiment of the invention, a point on thedevice corresponds to a single line in 3D space and the same physicalpoint on the device is followed along several frames, thus creatingseveral temporally-dependent 3D lines.

According to an exemplary embodiment of the invention, several physicalpoints on the same device and at a given instant are used creatingseveral spatially-dependent 3D lines.

According to an exemplary embodiment of the invention, a combination ofboth methods is provided, i.e. several physical points on the device aretracked along time.

According to an exemplary embodiment of the invention, to a given pointseen in a projection, there is a set of possible 3D points that havecreated the 2D projected point, i.e. for a given geometry. This set is a3D line. All the points on this line participate to the projection, butin case only some of them are really radio-absorbent, according to theinvention, those very absorbent points are referred to as the 3Doriginating points of the 2D projected point.

For example, a line in space potentially may intersect several segmentsof the tubular structure, for example in several vessels. More pointsare acquired, for example, temporal or spatial different points.Ambiguity is thus removed by determining which segment, or vessel, hasthe highest probability to enclose the device.

According to an exemplary embodiment of the invention, the oneprojection geometry is a monoplane X-ray fluoroscopy acquisition.

According to an exemplary embodiment of the invention, the device lieswithin a segment of the tubular structure throughout the navigationalprocedure.

According to an exemplary embodiment of the invention, the device canonly lie within a couple of possible tubular segments. Further, theprobability is maximized by the number of intersections of determineddevice lines and tubular segments; wherein the intersections correspondto points.

According to an exemplary embodiment of the invention, the device has atip and the tip is localized in the tubular structure complexity with anaccuracy of about or less that the tubular width, for example, unlessthe device is bent and leaning against either side of the tubularsegment.

According to an exemplary embodiment of the invention, the tip islocalized in the tubular structure complexity in the length direction ofthe tubular segment and not within the width direction.

According to an exemplary embodiment of the invention, theinterventional device is at least partially radiopaque to X-rays.

According to an exemplary embodiment of the invention, theinterventional device is a guide wire.

According to an exemplary embodiment of the invention, theinterventional device is a endo-prosthesis delivery system such as astent delivery system with its balloon and locating markers. This kindof devices might be used in coronary or Neuro interventions (Neurostents, flow diverters, coils).

According to an exemplary embodiment of the invention, the tubularstructure comprises vessels.

According to an exemplary embodiment of the invention, navigation isprovided in 2D.

According to an exemplary embodiment of the invention, the tubularstructure provides only a few locations in space for the interventionaldevice to be enclosed within the tubular structure which, for example,has a sparse structure.

According to an exemplary embodiment of the invention, the 3D dataset iscreated from acquired 2D projections, for example X-ray angiograms. Forexample, the 2D projections are acquired in form of a rotationalangiographic scan.

According to an exemplary embodiment of the invention, the 3D dataset or3D representation is acquired from a CT scanner, MRI, ultrasound or thelike.

According to an exemplary embodiment of the invention, the at least one2D X-ray image is registered such that the spatial orientation andposition of the 3D volume of the 3D dataset corresponds to the spatialorientation and position of the tubular structure of the object ofinterest in the X-ray.

According to an exemplary embodiment of the invention, for registration,ridgeness information in the 2D image and in the 3D volume is matched.

According to an exemplary embodiment of the invention, for registration,also the X-ray system's geometry information is used.

According to an exemplary embodiment of the invention, the 2D X-rayfluoroscopy image data is acquired with injected contrast agent.

According to an exemplary embodiment &the invention, the 2D deviceposition and related 3D position are continuously tracked during thenavigation process and navigational information is provided to the userin real-time.

According to an exemplary embodiment of the invention, the local 3Dparameters comprise parameters of the tubular segment of the tubularstructure surrounding the interventional device.

For example, in case the tubular structure comprises vessels, the local3D parameters comprise quantities typically derived with quantitativecoronary analysis (QCA), like vessel diameter, lumen area, segmentlength and bifurcation angles.

Depending on the type of interventional procedure, an addition tothree-dimensional parameters, also other local parameters relating tothe determined point in space of the tubular structure can also beprovided as additional information to the user. For example,characteristics or features of the vessel walls, for example tissue likecalcifications, can also be indicated or transmitted as information tothe user.

According to an exemplary embodiment of the invention, the local 3Dparameters comprise parameters of the tubular structure in the vicinityof the interventional device.

According to an exemplary embodiment of the invention, the local 3Dparameters comprise parameters of the tubular structure in as spatialregion around the interventional device.

According to an exemplary embodiment of the invention, the extension ofthe spatial region is predetermined.

According to an exemplary embodiment of the invention, the extension ispredetermined according to the chosen device.

According to an exemplary embodiment of the invention, the extension isset by a user.

According to an exemplary embodiment of the invention, step h) comprisesdisplaying the navigational information to the user.

According to an exemplary embodiment of the invention, the local 3Dparameters of the tubular structure are extracted from the previouslyacquired 3D dataset.

According to an exemplary embodiment of the invention, step e) comprisescomputing probabilities for different segments of the tubular structure;and maximizing accumulated probability from the different probabilitiesto determine in which segment of the tubular structure the device may belocated. Further, on behalf of the accumulated probability informationis gathered in space from the 3D dataset.

In order to map the 2D position to a position in the 3D data set, or inother words to find a 3D position for the 2D position, the chance orpossibility for the two-dimensional position is computed by transformingthe two-dimensional position into a line in the 3D data set. Then, theprobability or chance for a point along the line to be the actual 3Dposition is computed by reducing the possible positions along the lineto be matching with one of the tubular segments that are defined in the3D data set. Of course, this leads to numerous several segments intowhich the device can fit. For example, if this is followed in time, theprobability for several vessels is maximized thus leading to accumulatedprobabilities.

In other words, a number of computational steps or procedures,comprising several probability computation loops, provide geometricalinformation with a maximized probability to represent the actualthree-dimensional position.

According to an exemplary embodiment of the invention, a device which ispoint-wise visible under X-ray fluoroscopy is temporally detected as twodifferent points; and in step e) probabilities arc computed for thepoints to be located in a number of segments of the tubular structureand the probabilities are maximized to reduce the number of segments.Further, a segment with the highest probability is determined to beenclosing the device.

According to an exemplary embodiment of the invention, before step h),the navigational information is converted into graphical advisoryinformation. Further, step h) comprises adapting acquired image data ofthe region of interest on behalf of the navigational information anddisplaying the adapted image data to the user.

According to an exemplary embodiment of the invention, the 2D X-rayimage data is transformed into enhanced 2D image data by superimposingthe graphical advisory information with the 2D X-ray image data and theenhanced 2D image data is displayed to the user.

According to an exemplary embodiment of the invention, the navigationalinformation is provided to the user while displaying the acquired 2DX-ray image.

According to an exemplary embodiment of the invention, 3D information isshown in 2D images.

According to an exemplary embodiment of the invention, 3D image data isgenerated from the previously acquired 3D dataset and the 3D image datais transformed into enhanced 3D image data by integrating the graphicaladvisory information. Further, the enhanced 3D image data is displayedto the user.

According to an exemplary embodiment of the invention, step f) comprisesdetermining the orientation of the surrounding tubular structure; stepg) comprises determining the orientation of the device in relation tothe surrounding tubular structure; and step h) comprises displaying anorientation indicator.

For example, when guiding a catheter or a wire tip through a vesseltree, it is important to get a good perception of the local vessel shapein three dimensions, in particular when confronted to strong out ofplane bending or complex tortuosity. The usual three-dimensional roadmapping technique provides a good projected road map in the X-ray fluoroplane, but is without depth information or at least less informativewhen it comes to the depth direction. When back-projecting the deviceinto the 3D reconstructed vessel tree, the disadvantage is that thisentails referring to a reconstructed and somewhat artificial viewingmode. Another serious problem is that three-dimensional data andtwo-dimensional projecting live views do not fuse very easily ornaturally. By providing a very simple depth indication, such as anorientation vector, at the device location, this using of a device as apointer to 3D data leads to a visualization that can easily be blendedwith the live image and does not clutter the fluoroscopy plane, whichcan thus stay as clear and unambiguous as possible. Another advantage isthat, apart from the device tracking and registration steps alreadymentioned, one has simply to get orientation information from thethree-dimensional data which does not require actual segmentation. Thisprovides advantages concerning computational power and time required inthe system.

According to an exemplary embodiment of the invention, the orientationindicator is a depth indicator indicating the depth of the tubularstructure.

According to an exemplary embodiment of the invention, the orientationindicator is an orientation vector.

According to an exemplary embodiment of the invention, the navigationalinformation comprises information about the tubular structure, forexample one or several of the group of diameter, lumen area, tissue,segment length, bifurcation positions and bifurcation angles.

According to an exemplary embodiment of the invention, these tubularparameters are derived by segmenting the tubular structure andsurrounding structures.

According to an exemplary embodiment of the invention, the segmentationis performed with the 3D dataset or 3D volume beforehand.

According to an exemplary embodiment of the invention, the segmentationis performed on the spot using the device location in the 3D dataset asa trigger for local automatic tubular structure segmentation.

According to an exemplary embodiment of the invention, step g) comprisestransforming the determined 3D parameters of the tubular structure intographical information; and step h) comprises displaying the graphicalinformation.

According to an exemplary embodiment of the invention, step g) comprisesidentifying optimal viewing direction for the segment of the tubularstructure surrounding the interventional device; determining a deviationfactor of current viewing direction of the X-ray imaging device inrelation to the optimal viewing direction; and determining a movementfactor for optimal viewing; and step h) comprises moving the X-rayimaging device in relation to the object for optimal viewing.

Having an optimal view angle of the device which is being navigatedthrough, for example, a vascular structure decreases the chance ofmisinterpretation on the side of the user due to a minimallyforeshortened or even unforeshortened view in which no or at least onlya minimum number of vessels overlap. For example, in case of a C-arm,the C-arm needs to be positioned manually by the operator for an optimalview. This requires full concentration and also experience by the userwhich has further disadvantages with respect to the duration of aninterventional procedure. For example, the derived optimal viewing anglecan be used to steer the C-arc of an X-ray system to the optimal viewingangle of the vessel segment pointed to by the device. This would thenfacilitate the interventional procedure, because the information to theuser would be presented in an optimized way, i.e. better detectable andeasier readable image information. This also means relieve for the user,since he or she can grasp the information in a shorter time, thusproviding certain economical benefits.

For example, when navigating the guide wire through neuro vessels to theregion of interest, the guide wire tip can be used as a pointer. Duringthe neuronavigation process, the C-arc can be steered in real-timethrough the optimal viewing angles of the vessel segments through whichthe tip advances. In that way, for example, a good view of the devicecan be maintained while patient dose can be reduced.

According to an exemplary embodiment of the invention, the optimalviewing direction is identified for the determined 3D position of theinterventional device with respect to the tubular structure.

According to an exemplary embodiment of the invention, the X-ray imagingdevice and the object are moved in relation to each other according tothe determined movement factor to acquire further 2D X-ray fluoroscopyimage data.

According to an exemplary embodiment of the invention, the X-ray imagingdevice is steered to the optimal viewing angle.

According to an exemplary embodiment of the invention, the X-ray imagingdevice is a C-arm and wherein for the optimal viewing direction arotating or viewing angle is determined as determined movement factor;and the C-arm is rotated according to viewing angle to acquire further2D X-ray fluoroscopy image data.

According to an exemplary embodiment of the invention, in an optimalviewing direction, foreshortening of the tubular structure at thelocation of the device position is minimal.

According to an exemplary embodiment of the invention, in an optimalviewing direction, overlap of the tubular structures at the location ofthe device position is minimal.

According to an exemplary embodiment of the invention, in an optimalviewing direction, the X-ray dose to the patient and/or the clinicalstaff is minimal.

According to an exemplary embodiment of the invention, the optimalviewing angle is defined by different parameters which parameters arebeing weighed differently depending on the phase of the interventionalprocedure.

According to an exemplary embodiment of the invention, during guide wirenavigation, the dose parameters have the largest weight whereas duringlesion treatment, foreshortening and overlap have the largest weight.

According to an exemplary embodiment of the system according to theinvention, the processing unit is adapted to convert the navigationalinformation into graphical advisory information. The processing unit isalso arranged to adapt acquired image data of the region of interest onbehalf of the navigational information. A display is connected to theinterface, the display being adapted to display the adapted image datato the user.

According to an exemplary embodiment of the invention, the processingunit is adapted to transform the 2D X-ray image data into enhanced 2Dimage data by superimposing the graphical advisory information with the2D X-ray image data. The display is arranged to display the enhanced 2Dimage data.

According to an exemplary embodiment of the invention, the processingunit is adapted to generate 3D image data from the previously acquired3D dataset and to transform the 3D image data into enhanced 3D imagedata by integrating the graphical advisory information. The display isarranged to display the enhanced 3D image data.

According to an exemplary embodiment of the invention, the processingunit is adapted to determine the orientation of the surrounding tubularstructure; and to determine the orientation of the device in relation tothe surrounding tubular structure. The display is arranged to display anorientation indicator.

According to an exemplary embodiment of the invention, the processingunit is adapted to identify optimal viewing direction for the segment ofthe tubular structure surrounding the interventional device and todetermine a deviation factor of current viewing direction of the X-rayimaging device in relation to the optimal viewing direction. Theprocessing unit is further adapted to determine a movement factor foroptimal viewing. The X-ray image acquisition device is adapted to bemoved in relation to the object for optimal viewing.

In another exemplary embodiment of the present invention, a computerprogram or a computer program element is provided that is characterizedby being adapted to execute the method steps of the method according toone of the preceding embodiments, on an appropriate system.

The computer program element might therefore be stored on a computerunit, which might also be part of an embodiment of the presentinvention. This computing unit may be adapted to perform or induce aperforming of the steps of the method described above. Moreover, it maybe adapted to operate the components of the above described apparatus.The computing unit can be adapted to operate automatically and/or toexecute the orders of a user. A computer program may be loaded into aworking memory of a data processor. The data processor may thus beequipped to carry out the method of the invention.

This exemplary embodiment of the invention covers both, a computerprogram that right from the beginning uses the invention and a computerprogram that by means of an up-date turns an existing program into aprogram that uses the invention.

Further on, the computer program element might be able to provide allnecessary steps to fulfill the procedure of an exemplary embodiment ofthe method as described above.

According to a further exemplary embodiment of the present invention, acomputer readable medium, such as a CD-ROM, is presented wherein thecomputer readable medium has a computer program element stored on itwhich computer program element is described by the preceding section.

However, the computer program may also be presented over a network likethe World Wide Web and can be downloaded into the working memory of adata processor from such a network. According to a further exemplaryembodiment of the present invention, a medium for making a computerprogram element available for downloading is provided, which computerprogram element is arranged to perform a method according to one of thepreviously described embodiments of the invention.

It has to be noted that embodiments of the invention are described withreference to different subject matters. In particular, some embodimentsare described with reference to method type claims whereas otherembodiments are described with reference to the device type claims.However, a person skilled in the art will gather from the above and thefollowing description that, unless otherwise notified, in addition toany combination of features belonging to one type of subject matter alsoany combination between features relating to different subject mattersis considered to be disclosed with this application. However, allfeatures can be combined providing synergetic effects that are more thanthe simple summation of the features.

It has to be noted that exemplary embodiments of the invention aredescribed with reference to different subject matters. In particular,some exemplary embodiments are described with reference to apparatustype claims whereas other exemplary embodiments are described withreference to method type claims. However, a person skilled in the artwill gather from the above and the following description that, unlessother notified, in addition to any combination of features belonging toone type of subject matter also any combination between featuresrelating to different subject matters, in particular between features ofthe apparatus type claims and features of the method type claims isconsidered to be disclosed with this application.

BRIEF DESCRIPTION OF THE DRAWINGS

The aspects defined above and further aspects, features and advantagesof the present invention can also be derived from the examples ofembodiments to be described hereinafter and are explained with referenceto examples of embodiments, but to which the invention is not limited.The invention will be described in more detail hereinafter withreference to the drawings.

FIG. 1 schematically shows a system for navigating an interventionaldevice according to the invention;

FIG. 2 schematically shows the basic steps of a method for navigating aninterventional device according to the invention;

FIG. 3 schematically shows further sub-steps of a further exemplaryembodiment of the method of FIG. 2;

FIG. 4 schematically shows further sub-steps of the method of FIG. 2;

FIG. 5 schematically shows further sub-steps of a further exemplaryembodiment of the method of FIG. 2;

FIG. 6 schematically shows a further exemplary embodiment of the methodof FIG. 2;

FIG. 7 schematically shows further sub-steps of a further embodiment ofthe method of FIG. 2;

FIG. 8 schematically shows an acquired 2D X-ray fluoroscopy image with adetected device;

FIG. 9 schematically shows an image plane with the device of FIG. 8 inrelation to a device plane;

FIG. 10 shows an enhanced 2D X-ray image with one exemplary embodimentof navigational information provided to the user;

FIG. 11 schematically shows a further exemplary embodiment of thenavigational information provided to the user;

FIG. 12 schematically shows a further exemplary embodiment of thenavigational information provided to the user;

FIG. 13 schematically shows a further exemplary embodiment of thenavigational information provided to the user;

FIGS. 14 to 18 show FIGS. 8, 10, 11, 12 and 13 with an X-ray imageinstead of the schematic representation of an X-ray image for betterunderstanding.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 schematically shows a system 10 for navigating an interventionaldevice 12 within a tubular structure of an object, for example a patient13. As an example, the interventional device is a guide-wire forpercutaneous coronary interventions. The guide wire has a tip, indicatedwith reference number 14, but not further shown. The system 10 comprisesan X-ray image acquisition device 16 with a source of X-ray radiation 18provided to generate X-ray radiation. A table 20 is provided to receivea subject to be examined, for example the patient 13. Further, the X-rayimage acquisition device 16 comprises a detection module 22 locatedopposite the source of X-ray radiation 18, i.e. during the radiationprocedure, the subject or patient 13 is located between the source ofX-ray radiation 18 and the detection module 22. The latter is sendingdata to a control unit or processing unit 24 connected to the X-rayimage acquisition device 16 by a cable connection 26. Of course, thecable connection 26 can also be provided in form of a wirelessconnection (not shown). The interventional device 12 is connected to aninterface 28, which connection is not shown in FIG. 1 and which can beimplemented as a wire-based or as a wireless connection. The interface28 is connected to the processing unit 24 and the image X-ray imageacquisition device 16 by connections 29 and 30 respectively. Further, adisplay 32 is connected to the processing unit 24.

The X-ray image acquisition device 16 is provided as a so-called C-typeX-ray image acquisition device where the X-ray source 18 and thedetection module 16 are arranged on opposing ends of a C-arm 33. TheC-arm is rotatably mounted around a horizontal axis indicated as Z-axis.The C-arm can further be rotated in a circular or semicircular formindicated by arrow 34. Further, according to the example shown, theC-arm 33 is mounted to a support 36 suspended from a ceiling 40, whereinthe support is rotatable around a vertical axis indicated as X-axis.Thus, X-ray images can be acquired from different directions ofdifferent regions of interest of the patient 13.

The interface device 28 is arranged to input information by the user.

It is noted that the example shown as a C-type X-ray image acquisitiondevice, although the invention also relates to other types of X-rayimage acquisition devices, such as CT systems. Of course, as an X-raysource a much more simplified C-arm device can be used than the oneshown in FIG. 1.

The X-ray image acquisition device 16 is adapted to acquire 2D X-rayfluoroscopy image data in one projection geometry of a region ofinterest of the tubular structure, in the case shown, of a region ofinterest of the patient 13.

The processing unit 24 is adapted to detect the interventional device 12in the 2D X-ray image and to determine the 2D position of theinterventional device 12 in the 2D X-ray image. The processing unit 24is further adapted to register the at least one 2D X-ray image with apreviously acquired 3D data set of the region of interest of the patient13.

The previously acquired 3D data set is stored in a memory (not shown) ofthe processing unit 24.

The processing unit 24 is further adapted to map the determined 2Dposition of the interventional device 12 to a position in the 3D dataset and to extract local 3D parameters of the tubular structure, forexample the vessel structure of the patient, at the position of theinterventional device 12. The processing unit 24 is further adapted togenerate navigational information on the half of the determined 3Dposition of the interventional device 12 and the extracted local 3Dparameters.

The interface 28 is adapted to provide the navigational information tothe user.

The procedure according to the invention to be used with the abovedescribed system 12 is described in more detail below.

As can be seen from FIG. 1, the method for navigating the interventionaldevice 12 within a tubular structure of an object, for example thevessel structure of the patient 13, comprises the following steps.First, in an acquisition step 112, 2D X-ray fluoroscopy image data 113is acquired in one projection geometry of a region of interest of thetubular structure. Second, in a detection step 114, the interventionaldevice 12 is detected in the 2D X-ray image acquired in acquisition step112. Then, in a determining step 116, the 2D position of theinterventional device 12 is determined in the 2D X-ray image. Next, in aregistration step 118, the at least one 2D X-ray image is registeredwith a previously acquired 120 3D data set 121 of the region of interestof the tubular structure. Next, in a mapping step 122, the determined 2Dposition of the interventional device 12 is mapped to a position in the3D data set 121. Next, in an extraction step 124, local 3D parameters125 of the tubular structure are extracted at the position of theinterventional device 12. Further, in a generating step 126,navigational information 127 is generated on behalf of the determined 3Dposition of the interventional device 12 and the extracted local 3Dparameters 125. Then, in a providing step 128, the navigationalinformation 127 is provided to the user.

For example, navigating the interventional device 12 comprises guidingthe user, for example a physician such as a surgeon, performing amedical procedure.

For example, the 2D X-ray fluoroscopy image data 113 comprises asequence of two images with the same projection geometry. The 3Dposition is mapped 122 by extracting a determined point of theinterventional device 12 in the two 2D images.

As an example, one point on the interventional device 12 in projectioncorrespond to a line in 3D space and the device 12 moves between twoprojections, for example during two X-ray fluoroscopy images. The linein space potentially may be located in several segments of the tubularstructure, such as vessels of the patient 13. When more points areacquired, for example in a temporal or spatial manner, ambiguity isremoved by determining which segment or vessel has the highestprobability to enclose the device 12 (not further shown in detail).

As an example, the one projection geometry is a monoplane X-rayfluoroscopy acquisition.

It is noted, that according to the exemplary embodiment, theinterventional device 12 lies within a segment of the tubular structurethroughout the navigational procedure. Hence, the device 12 can only liewithin a couple of possible tubular segments. For example, theprobability is maximized by the number of intersections of determineddevice-originating 3D lines and tubular segments, wherein theintersections correspond to points.

The device 12 has a tip and the tip is localized in the tubularstructure complexity with an accuracy of about or less than the tubularwidth, unless the device 12 is bent and is leaning against either sideof the tubular segment. The tip is localized in the tubular structurecomplexity in the length direction of the tubular segment and not withinthe width direction.

Needless to say, but the interventional device 12 is at least partiallyradiopaque to X-rays such that it can be detected in X-ray images. Forexample, the interventional device is a guide wire. As another example,the interventional device can comprise a biopsy needle or theinterventional device 12 is a balloon and stent system for stenosis oraneurysm treatment. It can also be a coil or a flow diverter. It can beany kind of endo-prosthesis, steering device, endo-protection device ormeasuring device.

In general, the tubular structure such as a vessel structure, has asparse structure such that the tubular structure provides a fewlocations in space for the interventional device 12 to be enclosedwithin the tubular structure.

The 3D data set 121 is, for example, created from acquired 2Dprojections, for example X-ray angiograms. For example, the 2Dprojections for generating the 3D data set are acquired in form ofrotational angiographic scan.

According to another exemplary embodiment, not further shown, the 3Ddata set or 3D representation is acquired from a CT scanner, an MRIsystem, ultrasound system or the like.

In the registration step 118, the at least one 2D X-ray image isregistered such that the spatial orientation and position of the 3Dvolume of the 3D data set 121 corresponds to the spatial orientation andposition of the tubular structure of the object of interest in the X-rayradiation. For example, for registration, ridgeness information in the2D image and in the 3D volume is matched. In the case of weak motions,such as in the case of Neuro interventions, only geometrical informationcan be used for this registration process.

The method according to the invention provides the advantage, thataccording to an exemplary embodiment, the 2D device position and related3D position are continuously tracked during the navigation process andnavigational information 127 is provided 128 to the user in real-time.

For example, the local 3D parameters 125 comprise parameters of thetubular segment of the tubular structure surrounding the interventionaldevice 12.

For example, this refers to the vicinity of the interventional device 12or, in other words to a spatial region around the interventional device12. For example, the extension of the spatial region is predetermined,for example according to the chosen device or set by a user.

According to another exemplary embodiment of the method described above,the step of mapping 122 comprises a computation step 130 whereprobabilities are computed for different segments of the tubularstructure, as indicated in FIG. 3. Then, in a maximizing step 132,accumulated probability is maximized from the different probabilities todetermine 134 in which segment of the tubular structure the device maybe located. Further, on behalf of the accumulated probability,information is gathered 136 in space from the 3D data set 121.

As an example, not further shown in detail, a device, which is pointwisevisible under X-ray fluoroscopy is temporarily detected as two differentpoints. According to this embodiment, in the step of mapping,probability are computed for the points to be located in a number ofsegments of the tubular structure and the probabilities are maximized toreduce the number of segments and a segment with the highest probabilityis determined to be enclosing the device.

According to a further exemplary embodiment illustrated in FIG. 4,before the providing step 128, the navigational information 127 isconverted 138 into graphical advisory information 140. The providingstep 128 comprises adapting 142 acquired image data of the region ofinterest on behalf of the navigational information and displaying 144the adapted image data to the user.

According to one example illustrated in FIG. 5, the 2D X-ray image data113 is transformed into enhanced 2D image data 143 a by superimposingthe graphical advisory information 140 with a 2D X-ray image data 113and the enhanced 2D image data 143 a is displayed 144 to the user.

According to another exemplary embodiment, 3D image data is generatedfrom the previously acquired 3D data set 121 and the 3D image data istransformed into enhanced 3D image data 143 b by integrating thegraphical advisory information 140. The enhanced 3D image data 143 b isdisplayed 144 to the user. (see also FIG. 5)

According to a further exemplary embodiment shown in FIG. 6, theextracting step 124 comprises determining 148 the orientation of thesurrounding tubular structure. The generating step 126 comprisesdetermining 150 the orientation of the device 12 in relation to thesurrounding tubular structure. Further, the providing step 128 comprisesdisplaying 152 an orientation indicator 154.

For example, the orientation indicator 154 is a depth indicatorindicating the depth of the tubular structure.

As a further example, the orientation indicator 154 is an orientationvector.

According to a further exemplary embodiment of the method according tothe invention, shown in FIG. 7, the generating step 126 comprisesidentifying 156 optimal viewing direction 158 for the segment of thetubular structure surrounding the interventional device 12. Then, in adetermining step 160, a deviation factor 162 of the current viewingdirection of the X-ray imaging device 16 in relation to the optimalviewing direction 158 is determined. Next, in another determining step164, a movement factor 166 is determined for optimal viewing. Theproviding step 128 comprises moving 168 the X-ray imaging device 16 foroptimal viewing.

For example, the optimal viewing direction 158 is identified for thedetermined 3D position of the interventional device 12 with respect tothe tubular structure.

For example, the X-ray imaging device 16 and the object, that is thepatient 13 are moved in relation to each other according to thedetermined movement factor to acquire further 2D X-ray fluoroscopy imagedata. For example, when using a C-arm, the C-arm provides for rotationalmovement and the table 20 is movable in a longitudinal direction toprovide movement in this direction. Of course, the table can also bemovable in a direction perpendicular to the longitudinal axis to providea system with movement possibilities in all directions.

In an optimal viewing direction, foreshortening of the tubular structureat the location of the device position is minimal. According to anotherexample, in an optimal viewing direction, overlap of the tubularstructure at the location of the device position is minimal.

According to a further exemplary embodiment, that can of course becombined with the above-mentioned embodiments, in an optimal viewingdirection, the X-ray dose to the patient and/or the clinical staff isminimal.

According to an exemplary embodiment, not further shown, the optimalviewing angle is defined by different parameters which parameters arebeing weighed differently depending on the phase of the interventionalprocedure. For example, during guide wire navigation, the doseparameters have the largest weight whereas during lesion treatment,foreshortening and overlap have the largest weight.

Further, FIGS. 10 to 12 schematically show different examples fornavigational information being provided 128 to the user.

FIG. 8 schematically shows an acquired 2D X-ray image 213 with a device212 of which the device tip 214 is detected and indicated with agraphical marker. The X-ray image shows anatomical information about theobject, e.g. the patient 13. As can be seen, the X-ray image shows apart of a tubular structure, i.e. a vessel structure 215. Depending onthe type of procedure, the tip can also be indicated in white, colour orin a dotted line, whatever provides the best perceptibility.

For a better understanding, FIG. 9 schematically shows a perspectiveview of an image plane 213 p in a geometrical coordinate systemindicated by a X-axis, a Y-axis and a Z-axis. The image plane 213 p inwhich the image 213 is acquired is defined by the X-axis and the Y-axis.In other words, the image 213 is the view from so to speak above undersome tilted viewing in FIG. 9. The device tip 214 as seen in the imageplane 213 p is indicated with a dotted line 214 p. The device tip 214 islocated in a plane being defined as device plane 216 p. The device plane216 p is defined by the Z-axis for indicating the depth in the image anda vector 218 starting at O, which is the starting point of the devicetip 214 in the image plane 213 p, which vector is directed towards M asa line arranged in the horizontal plane 213 p including the front end ofthe tip 214. The actual device is indicated by a line 220. As can beseen, the line 214 p is a projection of the device tip line 220 in thehorizontal plane 213 p, indicated by a connecting line 219 connectingthe tip in projection and the tip in its real depth orientation. Thedepth vector of the device tip 214 is indicated with a vector 222.

The device plane follows the device when moving the device 12 inrelation to the patient 13.

This information of the depth direction of the device tip 214 serves asthe basis for the navigational information to be provided to the user.

To provide the user with the depth information for steering the device212, FIG. 10 shows an exemplary embodiment in which the 2D X-ray image213 is warped to a warped 2D image 224 be arranged in the image plane213 p. The warped image 224 provides the same information as areal-world image to the clinician, only in a distorted or warped way,thus giving the impression of a spatial or 3D arrangement withoutleaving the graphical means used in 2D images. The coordinate systemXYZ, the indication of the image plane and the indication of the deviceplane provide a good impression of the orientation of the device tip 214together with depth vector 222. Hence, FIG. 10 shows an enhanced 2Dimage 223 as navigational information.

Even better information perception can be achieved when applying acertain opacity to the layer of the 2D image (not shown). Then, a betterdifferentiation is possible between a device pointing upwards out of theimage plane and a device pointing downwards (as in the figure).

According to an exemplary embodiment (not shown), colors are used forthe coordinate system, the image plane and the device plane as well asfor the device tip and the depth vector.

Another exemplary embodiment is shown in FIG. 11 where a device tip 314is detected in an acquired 2D X-ray fluoro image 313, the device tipindicated by a white line for example. Of course, on a color display,the device tip can be shown in color, for example in red. A miniatureversion of the coordinate system of FIG. 9, or pictogram 321, is shownwithin the image 313 thus providing an enhanced 2D image 323. The actualorientation of the device in relation to the image plane is indicatedwith a depth vector 322 acting as navigational information.

Another exemplary embodiment is shown in FIG. 12. Instead of the 3Dcoordinate system, a further reduced pictogram 421 is shown in an X-rayimage 413, the pictogram 421 comprising a Z-axis and the axis O-M withinthe image plane, i.e. the view is perpendicular to the image planeitself. This navigational information is shown within a 2D X-ray image413 where the device tip is detected and indicated with a white markedline 414, which, of course, can also be displayed in color. The depthorientation of the device tip is indicated by a depth vector 422 inrelation to the reduced graphical coordinate system. Accordingly, anenhanced 2D image 423 is provided to the user.

Another exemplary embodiment is shown in FIG. 13. The device tip isindicated with a color-coded marker 514. The color-coding is relating toa color space as, for example known from Johannes Itten or Philipp OttoRunge. Basically, a spectrum of colors is associated with surface partsof a sphere. A direction vector, or orientation vector, arranged inspace according to the determined orientation will thus point atdifferent parts with different colors. Hence, the depth vector asdescribed above, is replaced by a color depending on its direction. Inone exemplary embodiment, the color only refers to a vector directionwithin a plane vertical to the image plane. In another exemplaryembodiment, the color also takes the horizontal angle into account,which of course is also visible on the image. For facilitating theunderstanding, a color coded sphere or band-like color coded space 520is shown as a pictogram within the 2D X-ray image 513. The orientationin space is indicated with an arrow 522 pointing at the color in whichthe device tip 514 is shown. Accordingly, an enhanced 2D image 523 isprovided to the user.

According to a reduced exemplary embodiment of the one described above,a simple color coding of [−pi/2, +pi/2] is provided, because the devicedirection is already known in projection. As an example, a color bar isprovided and the tip is directly colored with the respective color.

According to another exemplary embodiment, but which is not furthershown, 3D image data is generated from the previously acquired 3Ddataset. The 3D image data is transformed into enhanced 3D image data byintegrating the graphical advisory information in a similar way asdescribed above for the enhanced 2D X-ray images.

According to a further exemplary embodiment, not further shown, one ofthe above-mentioned examples is provided in colour for further or moredetailed navigational information.

By providing a system and a method according to the invention, the useris provided with easily comprehensible navigation information in agraphical world, that is in the 2D X-ray fluoroscopy images, which mostclinicians are familiar with. Thus, the user is provided with the realworld information he wishes to rely upon, that is the informationprovided in the actual X-ray fluoroscopy image, plus additionalnavigation information facilitating the steering or navigation of theinterventional device within the tubular structure.

FIGS. 14 to 18 show FIGS. 8, 10, 11 and 12 respectively with an X-rayimage instead of the schematic representation of an X-ray image forbetter understanding. For better visibility, the device tip is indicatedwith a white line in FIG. 14.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, such illustration and descriptionare to be considered illustrative or exemplary and not restrictive. Theinvention is not limited to the disclosed embodiments. Other variationsto the disclosed embodiments can be understood and effected by thoseskilled in the art in practicing a claimed invention, from a study ofthe drawings, the disclosure, and the dependent claims.

In the claims, the word “comprising” does not exclude other elements orsteps, and the indefinite article “a” or “an” does not exclude aplurality. A single processor or other unit may fulfill the functions ofseveral items re-cited in the claims. The mere fact that certainmeasures are re-cited in mutually different dependent claims does notindicate that a combination of these measures cannot be used toadvantage.

A computer program may be stored and/or distributed on a suitablemedium, such as an optical storage medium or a solid state mediumsupplied together with or as part of other hardware, but may also bedistributed in other forms, such as via the interne or other wired orwireless telecommunication systems.

Any reference signs in the claims should not be construed as limitingthe scope.

1. A system (10) for navigating an interventional device (12) within atubular structure of an object (13); comprising: an X-ray imageacquisition device (16); a processing unit (24); and an interface (28);wherein the X-ray image acquisition device (16) is adapted to acquire 2DX-ray fluoroscopy image data in one projection geometry of a region ofinterest of the tubular structure; wherein the processing unit (24) isadapted to detect the interventional device (12) in the 2D X-ray image;to determine the 2D position of the interventional device (12) in the 2DX-ray image; to register the at least one 2D X-ray image with apreviously acquired 3D dataset of the region of interest of the tubularstructure; to map the determined 2D position of the interventionaldevice to a position in the 3D dataset; to extract local 3D parametersof the tubular structure at the position of the interventional device;and to generate navigational information on behalf of the determined 3Dposition of the interventional device (12) and the extracted local 3Dparameters; wherein the interface (28) is adapted to provide thenavigational information to the user.
 2. The system according to claim1, wherein the processing unit (24) is adapted to convert thenavigational information into graphical advisory information; to adaptacquired image data of the region of interest on behalf of thenavigational information; and a display (32) is provided to display theadapted image data to the user.
 3. The system according to claim 1,wherein the processing unit (24) is adapted to determine the orientationof the surrounding tubular structure; and to determine the orientationof the interventional device (12) in relation to the surrounding tubularstructure; and wherein the display (32) is adapted to display anorientation indicator.
 4. The system according to claim 1, wherein theprocessing unit (24) is adapted to identify optimal viewing directionfor the segment of the tubular structure surrounding the interventionaldevice (12); to determine a deviation factor of current viewingdirection of the X-ray imaging device (16) in relation to the optimalviewing direction; and to determine a movement factor for optimalviewing; and wherein the X-ray image acquisition device (16) is adaptedto be moved in relation to the object for optimal viewing.
 5. A methodfor navigating an interventional device (12) within a tubular structureof an object, comprising the following steps: a) acquiring (112) 2DX-ray fluoroscopy image data (113) in one projection geometry of aregion of interest of the tubular structure; b) detecting (114) theinterventional device (12) in the 2D X-ray image; c) determining (116)the 2D position of the interventional device in the 2D X-ray image; d)registering (118) the at least one 2D X-ray image with a previouslyacquired (120) 3D dataset (121) of the region of interest of the tubularstructure; e) mapping (122) the determined 2D position of theinterventional device to a position in the 3D dataset (121); f)extracting (124) local 3D parameters (125) of the tubular structure atthe position of the interventional device (12); g) generating (126)navigational information (127) on behalf of the determined 3D positionof the interventional device (12) and the extracted local 3D parameters(125); and h) providing (128) the navigational information (127) to theuser.
 6. The method according to claim 5, wherein step e) comprisescomputing (130) probabilities for different segments of the tubularstructure; and maximizing (132) accumulated probability from thedifferent probabilities to determine (134) in which segment of thetubular structure the interventional device (12) may be located; whereinon behalf of the accumulated probability information is gathered (136)in space from the 3D dataset.
 7. The method according to claim 5,wherein before step h), the navigational information is converted (138)into graphical advisory information (140) and wherein step h) comprisesadapting (142) acquired image data of the region of interest on behalfof the navigational information and displaying (144) the adapted imagedata to the user.
 8. The method according to claim 5, wherein the 2DX-ray image data is transformed into enhanced 2D image data (143 a) bysuperimposing the graphical advisory information (140) with the 2D X-rayimage data (113); and wherein the enhanced 2D image data (143 a) isdisplayed (144) to the user.
 9. The method according to claim 5, wherein3D image data is generated from the previously acquired 3D dataset (121)and wherein the 3D image data is transformed into enhanced 3D image data(143 b) by integrating the graphical advisory information (140); andwherein the enhanced 3D image data (143 b) is displayed (144) to theuser.
 10. The method according to claim 5, wherein step f) comprisesdetermining (148) the orientation of the surrounding tubular structure;wherein step g) comprises determining (150) the orientation of thedevice in relation to the surrounding tubular structure; and whereinstep h) comprises displaying (152) an orientation indicator (154). 11.The method according to claim 5, wherein step g) comprises identifying(156) optimal viewing direction (158) for the segment of the tubularstructure surrounding the interventional device; determining (160) adeviation factor (162) of current viewing direction of the X-ray imagingdevice in relation to the optimal viewing direction; and determining(164) a movement factor (166) for optimal viewing; and wherein step h)comprises moving (168) the X-ray imaging device (16) in relation to theobject for optimal viewing.
 12. Computer program element for controllinga system according to claim
 1. 13. Computer readable medium havingstored the program element of claim 12.